The field of this invention relates to a post-tensioned concrete floor construction including an in-floor electrical wiring distribution system.
Post-tensioned concrete slab constructions have become commonly used in recent years. When used as a floor of an office building, this construction has inherent advantages over other types of floors because the strength of the concrete slab is improved along with a reduction in the thickness of the floor. In such a floor, a series of steel tendons extend across and are embedded in the concrete slab, and after the concrete has set, the tendons are placed under high tension in order to counteract the load stresses placed on the slab during use.
It has also been commonplace to provide an in-floor electrical wiring distribution system in other types of concrete floors of office buildings. A typical system of this nature includes a service outlet or fitting at each work station on the floor, and connections for electric power, telephones and data transmission at each service outlet. A series of cellular metal floor raceways are embedded in the slab and carry the wiring to the service outlets, and a trench, partially embedded in the slab, runs crosswise of the raceways and carries the wires to the raceways.
It will be apparent that a concrete slab, or a section of a slab, containing an in-floor distribution system as described must have embedded therein a large number of service outlets and raceways and at least one trench, and these components create voids in the concrete, and the voids reduce the strength of the slab. The voids are particularly large and critical at each location where the trench intersects the raceways. The trench extends across the upper surfaces of the raceways and consequently there is a doubly thick void at the intersections.
Heretofore, concrete slab floors have not been provided with both an in-floor distribution system and with post-tensioned tendons, and it is believed that there are a number of reasons for this. The loss of strength due to the voids in the slab produced by the distribution system components would normally be considered to prohibit this combination. Further, it would be considered that the distribution system components would interfere with the layout of the tendons in the slab, and the large number of embedded components would tend to produce honeycombing in the concrete.
It is a general object of this invention to provide a combination post-tensioned concrete floor and an in-floor electrical distribution wire system.